The invention relates to a device for controlling a power shunt circuit of a hybrid vehicle.
One field of application of the invention is hybrid road vehicles.
Document U.S. Pat. No. 6,486,632 describes a device comprising first and second inverters the DC sides of which are connected to a DC-voltage storage unit, the AC sides of which are designed to be connected to first and second polyphase electric machines, designed to be coupled to the mechanical drive of the vehicle, the first machine being capable of operating as a motor and the second machine being capable of operating as a generator for the shunting of power from the drive, the inverters also comprising chopping switches for the conversion between the DC sides and the AC sides, the device comprising a capacitor for filtering harmonics on the DC sides of the inverters and a unit for controlling the chopping switches, comprising a mode for controlling the chopping switches by pulse-width modulation of a carrier having an identical frequency for the inverters.
As is known in hybrid vehicles with power shunt and is represented in FIG. 1, two electric machines 3, 4 are connected to a mechanical drive 5 connected to the wheels 6, 7 on one side and to a power storage system 8 on the other side. Two inverters 1, 2 are used to control the machines 3, 4. For the shunting of power from the drive 5 when the drive 5 is driven by the internal combustion engine 9 of the vehicle, one of the machines must operate as a motor, while the other must operate as a generator. When the internal combustion engine is switched off, one of the two machines 3, 4 is used to operate the drive.
A common filtering capacitor C is usually mounted on the DC bus 10 between the two inverters 1, 2.
The inverters 1, 2 chop by opening and closing their DC-voltage switches in order to generate AC voltages which supply the machines 3, 4. This is called PWM (pulse-width modulation) chopping.
The high-frequency (a few kHz) chopping generates harmonics in addition to the effective fundamental on the currents of the machines, and in the same manner broadens the spectrum of the current generated on the DC bus 10.
The capacitor C filters most of these current harmonics in order to return a current as direct as possible to the storage element. The aging of the capacitor is sensitive to its heating, therefore to the RMS current passing through it. It is therefore of value to control the current to be filtered and its harmonic content.
Moreover, there are several possible chopping strategies for the inverters.